1. Field of the Invention
The present invention relates to a control apparatus that controls an AC motor.
2. Description of the Related Art
The wave height value of a fundamental wave voltage can be increased and thus, the motor output in a high rotation rate range can be increased by applying a single pulse rectangular wave voltage instead of a sine wave PWM voltage when applying a voltage to an AC motor with an inverter. The phase of the voltage applied to the motor can be controlled, but the amplitude of the voltage cannot be controlled in motor control implemented by using a rectangular wave voltage, since the voltage amplitude is determined in correspondence to a DC source voltage (DC link voltage) at the inverter. For this reason, the motor torque cannot be controlled accurately through such motor control.
There is a motor control apparatus in the related art that addresses this problem by estimating the motor torque with a torque estimating instrument and controlling the voltage phase based upon the deviation between a torque command value and the estimated value (see Japanese Laid Open Patent Publication No. 2000-050689). By utilizing this motor control apparatus, a torque which corresponds to the torque command value is obtained.